Thermal valve

ABSTRACT

A thermal valve in which heat is utilized to expand an actuator relative to a reference member. The actuator and reference member are interconnected at one end and one or the other carries a valve head on its opposite end whereby a differential in expansion moves the valve head from its seat. Ports are provided to conduct fluid between and in contact with the reference member and actuator and a baffle is disposed between the reference member and actuator to direct the fluid along the reference member for heat transfer therewith and to effect radiant heat shielding between the reference member and the actuator.

United States Patent Drexel 1 Mar. 21, 1972 54] THERMAL VALVE 3,022,0382/1962 Roubeau et a1 ..2s1/11 inventor: Charles F. Drexel Rolling HillsEstates 3,21 1,414 10/1965 Webb ..251/1 1 Primary Examiner-ArnoldRosenthal [73] Assignee: Tylan Corporation Att0rneyNilsson, Robbins,Wills &. Berliner [22] Filed: Mar. 2, 1970 [21 1 P 15,399 A thermalvalve in which heat is utilized to expand an actuator relative to areference member. The actuator and reference [52] U.S. Cl ..25l/11member are interconnected at one and one or the other 511 Int. Cl...F16k 31/04 F03g 7/06 Carries a Valve head its "PPOSite end whereby adifferential [58] Field of Search ........25 1/1 expansim the valve headfmm its are vided to conduct fluid between and in contact with the [56)References Cited reference member and actuator and a baffle is disposedbetween the reference member and actuator to direct the fluid UNITEDSTATES PATENTS along the reference member for heat. transfer therewithand to effect radiant heat shielding between the reference member3,229,956 l/1966 White ..251/11 and the actuator 3,465,962 9/1969Matullch et a1. ....251/l1 X 2,373,324 4/1945 Martin ..251/1l X 10Claims, 2 Drawing Figures Patented March 21, 1972 2 Sheets-Sheet 1INVENTOR.

CHARLES F. DREXEL.

Patented March 21, 1972 2 Sheets-Sheet 2 ZSQ CONTROL S/G/VQL I NVENTOKCHARLES F. DREXEL.

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cdttowyd 1 THERMAL VALVE FIELD OF THE INVENTION BACKGROUND AND SUMMARYOF THE INVENTION The electromechanical control and metering of fluidsgenerally requires utilization of complex servo valves, solenoids,torque motors and/or other sophisticated transducing instruments. Inorder to obtain accurate metering, it is often required to utilize aneedle-type valve having a sharply tapered valve head. The operation ofsuch valves can be impeded by contaminants in the fluid stream whichaccumulate along the sharp surface of the valve head to clog the valve.

The present invention provides an electromechanical transducer for valveoperation which does not utilize a motor, solenoid or other complexinstrumentality. The transducer is inexpensive, small, lightweight andrugged and yet works precisely and stably over a large range of fluidflow. Operation is accomplished without the utilization of movingpacking glands, seals or other such interface components and can bereadily hermetically sealed.

The present invention provides a transducer in which a valve assembly isoperated as a result of differential expansion of components of thetransducer when a heating element is actuated. In accordance herewith athermal valve is provided comprising a reference member and heatexpansible actuator, one or the other of these members carrying a valvehead for movement with respect to a valve seat. A heating element isdisposed in heat transfer relation with the actuator to expand theactuator relative to the reference member. The actuator and referencemember are interconnected in such manner that the expansion differentialeffects movement of the valve head-carrying member to move the valvehead out of or into its seat.

Means are provided defining inlet and outlet ports to conduct fluidbetween and in contact'with the reference member and actuator andthrough the valve assembly. A baffle is disposed between the referencemember and actuator to direct fluid along the reference member forefficient heat transfer therewith. The baffle also effects radiant heatshielding between the reference member and actuator to enhance theexpansion differential of these components. A housing is provided toenclose the valve which can be hermetically sealed to prevent fluid flowexcept through the inlet and outlet ports and thermal insulation can beprovided within the housing.

With respect to specific construction in one embodiment, the actuator istubular and formed long in proportion to its width. The reference memberis also in the form of an elongate, wider tube disposed coaxially aboutthe actuator and is secured to the actuator at one end thereof spacedfrom the valve assembly. A resistance wire is twisted and disposedwithin the actuator as a heating element. In another embodiment, theactuator is in tubular form and disposed coaxially about a referencerod. Resistance wire is coiled about the actuator as a heating element.In both cases a baffle tube is disposed coaxially between the actuatorand reference member.

A control signal to amplified and applied to the heating element so asto heat the actuator in proportion to the signal. Because a substantialsignal causes only slight expansion, and because operation of the valveis frictionless, the valve stroke can be made very small, on the orderof microinches. Accordingly, the valve seat can be made relatively largeand the valve head relatively flat, minimizing the danger of clogging.Since the heater element directly couples to an output amplifier, thereis no wear on the valve and virtually zero friction. Precise operationis obtained by forming the actuator and reference member of materialhaving substantially identical coefficients of heat expansion and withsubstantially identical effective lengths.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially schematiccross-sectional representation of a valve constructed in accordance withthe present invention; and

FIG. 2 is a partially schematic cross-sectional representation ofanother valve constructed in accordance with the present invention.

DETAILED DESCRIPTION As required, detailed illustrative embodiments ofthe invention are disclosed herein. However, it is to be understood thatthese embodiments merely exemplify the invention which may take manydifferent forms that are radically different from the specificillustrative embodiments disclosed. Therefore, specific structural andfunctional details disclosed herein are not to be interpreted aslimiting, but merely as a basis for the claims which define the scope ofthe invention.

Referring to FIG. 1, the thermal valve 10 therein illustrated includes anumber of concentric tubular members 12, 14, 16, and 18 of stainlesssteel which have various functions as hereinafter detailed. The outertubular member 12 constitutes a housing for the device and is threadedand then welded or brazed, as at 20, to a circular base 22. The base 22is formed centrally with a depending threaded stud 24 and defines a bore26 therethrough which is formed with progressively increased diameterportions 28 and 30 to define stepped shoulders 32 and 34 spaced from thebottom of the stud 24. The bottom surface of the base 22 defines anannular groove 36 around the stud 24 in which are disposed a pair ofconcentric metal O-rings 38 and 40. A conduit 42 is formed through thebase 22 from the groove 36 into the uppermost increased diameter portion30 of the bore 26. The valve 10 is designed to control or meter the flowof hydraeric fluid through a member 44 which defines passageways 46 and48 for the ingress and egress respectively of the fluid as indicated bythe arrows 50 and 52. The member 44 is formed with a threaded pocket 54for close fitting female engagement with the stud 24. The ingresspassageway 46 is formed through the surface 56 of the member 44 into theannular base groove 36. The egress passageway 48 is formed to open intothe base bore 26 'to receive fluid from the valve 10. When the stud 24is fully threaded into the pocket 54, the metal O-ring seals 38 and 40effectively prevent escape of fluid from the ingress passageway 46.

The innermost tubular member 18 is a thin elongate tube having, in thisillustration, an outer diameter of 0.015 inches and an inner diameter of0.010 inches. The tube 18 carries a valve head 58 at its lower end whichis formed to matingly engage a valve seat 60. The valve seat 60 iswelded or brazed as at 62 within the bore 26 abutting the shoulder 32.The tube 18 constitutes the actuator of the valve 10 and has disposedtherein a heater element in the form of resistance wire 64 which hasbeendoubled and twisted and dropped down into the tube 18 as shown at thebroken away portion in the drawing. As will be detailed hereinafter,heating of the resistance wire 64 effects an expansion or elongation ofthe actuator 18 which causes downward movement of the valve at 58 awayfrom its seat 60.

The next innermost tube 16 constitutes a baffle tube, the function ofwhich will be detailed hereinafter. The baffle tube 16 is disposedcoaxially on the actuator tube 18 and welded or brazed with the valveseat 60 to the base 22 as at 62.

Next, the tube 14 is disposed coaxially around the baffle tube 16 andconstitutes a reference tube as hereinafter explained. The referencetube 14 is disposed with its lower end resting on the shoulder 34 and isbrazed or welded as at 66 to the base 22. The lower end of the referencetube 14 defines an opening 68 which is positioned coincident with thebase conduit 42. The upper end of the reference tube 14 is formed withan indentation 70 to support a closure member 72 thereat. The closuremember 72 is formed with a central aperture 74 through which theactuator tube 18 extends. The closure member 72 is welded or brazed asat 76 to the reference tube 14 and to the top of the actuator tube 18 asat 78, such welding or brazing being effected to hermetically seal theengaging edge of the closure member with the respective edges of thereference tube 14 and actuator tube 18.

A close fitting tube 80 of styrofoam is disposed within the tubularhousing 12 and serves as thermal insulation for the valve. The open topof the tubular housing 12 is fitted with a lid 82 which is welded orbrazed as at 84 to the housing 12. The entire contact surfaces betweenthe housing 12 and the lid 82 and base 22 is welded or brazed so as toeffect external hermetic sealing of the valve.

The lid 82 is formed with an electrical terminal 86 therethrough. Priorto welding or brazing of the lid 82, an electrical wire 88 is broughtinwardly from the terminal 86, through an insulator 90 in a header 92,and soldered at 92 to one end of the resistance wire 64. The other endof the re sistance wire 64 is soldered at 94 to an electrical lead 96which is soldered at 98 to the header 92 which in turn is grounded byits connection to the closure member 72 affixed to the reference tube14.

In operation, the thermal valve is secured to the member 44 by threadingof the stud 24 into the threaded pocket 54 until the concentric O-rings38 and 40 are compressed sufficiently to effect hermetic sealing of thepassageway 46. As a result of its disposition around the stud 24, theinnermost O- ring 40 also effects hermetic sealing of the egresspassageway 48.

Liquid or gas to be controlled or metered is fed through the ingresspassageway 46 into the annular groove 36 and from there through thevalve base conduit 42 into the space 100 defined between the referencetube 14 and the baffle tube 16. The fluid then flows over the top of thebaffle tube 16 as shown by the arrows 102, and travels through theannular passage 104 defined between the inner surface of the baffle tube16 and the outer surface of the actuator tube 18, impinging against thevalve head 58.

Initially, the valve head 58 is closed against its seat 60, preventingfurther travel of the fluid. In order to meter the fluid into the egresspassageway 48, a control signal, indicated diagrammatically at 106 isfed along a line 108 to an amplifier 110 and from there along a line 112directly to the electrical terminal 86 and via the electrical wire 88 tothe resistance wire 64 within the actuator tube 18. By such applicationof an electrical signal, the resistance wire 64 heats up to increase thetemperature of the actuator tube 18 relative to the temperature of thereference tube 14 in proportion to the signal magnitude. Such heatingeffects a differential expansion between the actuator tube 18 and thereference tube 14 so that the actuator tube 18 expands with respect tothe reference tube 14, such expansion causing the length of the actuatortube 18 to increase to carry the valve head 58 away from its seat 60. Atthis point, the fluid can escape through the opening defined between thedisplaced valve at 58 and the seat 60, as indicated by the arrows 114,into the egress passageway 48 and from there to its predetermineddestination. As a signal of greater magnitude is transmitted, thetemperature of the actuator tube 18 rises as does the extent ofexpansion, resulting in the metering of a proportionally greater amountoffluid.

The baffle tube 16 is disposed relatively close to the inner surface ofthe reference tube 14 so as to direct the fluid along the reference tube14 thereby obtaining efficient heat transfer between the fluid andreference tube 14. If the initial condition of the valve is such thatthe valve head is spaced from its seat, then the fluid effects atemperature equilibrium between the reference tube 14 and actuator tube18. After the actuator tube 18 is heated, radiation therefrom would tendto heat up the reference tube 14 with a resultant decrease intemperature differential as a function of time. However, the baffle tube16 functions also as a radiant head shield which, together with the flowof fluid first past the inner surface of the reference tube, results inan equilibrium being rapidly established whereby the temperaturedifferential is accurately proportional to the applied control signalregardless of time during any period of continuous operation of thevalve.

It should be noted that the magnitude of heating required for properoperation of the valve is largely independent of the temperature of thefluid being metered, Opening of the valve is proportional to thetemperature difference between the reference and actuator tubes and thecoefficient of expansion of the actuator. The utilization of a baffletube 16 as described performs the several functions of directing inletfluid against the reference tube 14, shielding the reference tube 14from radiation and prevents heat transfer between the actuator andreference tube by natural convection at low flow rates. The space shouldbe small to achieve a high heat transfer coefficient between the inletgas and reference tube 14 so as to minimize power requirements. On theother hand, the space 104 is a compromise in that it must be large toreduce heat transfer between the actuator 18 and fluid, also in order tominimize power requirements, but is must be small enough to permitsufficiently rapid heat transfer from the actuator 18 when signal poweris removed to effect useful response.

Except for the electrical wiring and leads 88, 94, 96, and resistancewire 64, which are of standard materials for those functions, all thecomponents of the valve 10 can be constructed of stainless steel andthus a corrosion resistance valve is provided. However, any materialwhich is compatible with the fluid being metered can be utilizedprovided appropriate expansion coefficients are chosen for the variouscomponents. In this regard, if the temperature coefficient of linearexpansion of the material used for the actuator tube 18 is substantiallyidentical to the coefficient of the material used for the reference tube14, the relative positions of the valve head 58 and seat 60 will be thesame regardless of the temperature of the fluid being metered. This isparticularly important if it is desired that the valve head 58 beinitially closed against its seat 60. Furthermore, in order to obtainuniformity in the spacing between the valve head 58 at its seat 60 overa wide range of fluid temperatures, the actuator tube 18 and referencetube 14 should have substantially identical effective lengths. This isreadily accomplished by the foregoing structure wherein the base 22 aswell as other components are manufactured of material identical to theactuator tube 18 and reference tube 14, since as a result of the weldingor brazing of the reference tube 14 to the base 22, the effective lengthof the reference tube 14 and the actuator tube 18 are inherentlyidentical.

Referring now to FIG. 2, there is illustrated a thermal valve 210 ofalternative construction but which functions in the manner of thermalvalve 10 of FIG. 1 by generation of an expansion differential between anactuator member and a reference member. In this particular construction,the reference member is in the form of a thin elongate rod 214 andcarries the valve head 258 at its lower end. In contrast to the thermalvalve 10 of FIG. 1, in this embodiment the actuator is disposedexteriorally of the reference tube 214 and is in the form of anelongated tube 218 concentrically disposed about the reference tube 214.A heating coil of resistance wire 264 is wound around the actuator tube218 and is connected at one end by electrical wiring 288 to anelectrical terminal 286, and at its other end to a ground, indicatedschematically at 292.

The reference rod 214 can be hollow in the manner of the actuator tube18 of FIG. 1, or may be solid throughout, and is welded or brazed as at278 to a closure member 272 which, in turn, is welded or brazed as at276 circumferentially to the actuator tube 218. An annular base 222 isformed with a dependent threaded stud 224 and defines a bore 226therethrough. The bore is formed with an increased diameter upperportion 230 whereby a shoulder 234 is provided spaced from the bottom ofthe base 222. A baffle tube 216 is disposed on the shoulder 234 andwelded or brazed thereto as at 262. A valve seat 260, having a decreaseddiameter lower portion forming a shoulder 228, is disposed with theshoulder 228 bearing against the base shoulder 234 and is welded orbrazed as at 232 to the base 222.

In other respects, the valve 210 is constructed similarly to the valveof FIG. 1. Thus, an annular groove 236 is formed on the bottom surfaceof base 222 around the stud 224 and carries concentric O-rings 238 and240. A conduit 242 is defined through the base 222 into the bore 226.The actuator tube 218 is dimensioned to slide into the bore 226concentrically about the baffle tube 216, resting upon the shoulder 234.An opening is defined through the actuator tube 218 spaced from theshoulder 234 so as to coincide with the base circuit 242. The actuatortube 218 is then welded or brazed as at 266 to the base 222 to effect arigid, hermetically sealed structure.

A styrofoam insulating tube 280 is disposed on the support 222concentrically about the actuator tube 218. The support 222 is providedwith a threaded outer surface 290 which is engaged by the internalthreaded surface along the lower end of the tubular housing 212. A lid282 is disposed atop the housing 212 and hermetically sealed to thehousing by welding or brazing as at 284. The resistance wire 264 isconnected at one end to an electrical terminal 286 formed through thelid 282 by means of electrical wiring 288 and is connected at the otherend thereof to ground, indicated schematically at 292.

A member 244 is provided with is similar in construction to member 44depicted inFIG. 1 having passageways 246 and 248 defined therethrough inthe manner of the member 44 so that the passageway 248 is incommunication with the base bore 226 and the passageway 246 is incommunication, via the groove 236, with the base conduit 242. However,in this embodiment, the fluid to be metered is conducted initiallythrough the passageway 248 into the valve 210 and is conducted from thevalve 210 by means of the passageway 246 so that the flow of fluidthrough the member 244 is in a direction opposite to that of the flow offluid through the member 44.

In operation, a control signal is applied as indicated at 306 over aline 308 to an amplifier 310 and from there over a line 312 to theelectrical lead 286 so as to heat the resistance wire 264, therebycausing the actuator tube 218 to expand. Since the reference rod 214 isrigidly connected at its upper end to the actuator tube 218, by means ofthe closure member 272, the result of expansion of the actuator tube 218is that the reference rod 214 moves upwardly, carrying the valve head258 out of its seat 260. In this embodiment, the fluid flows from thepassageway 258 past the valve head 258 and is directed by the baffletube 216 against the surface of the reference rod 214, and from theretravels into the space 304 between the baffie tube 216 and in thesurface of the actuator tube 218, into the conduit 242 and out throughthe passageway 246 to its destination.

Note that in this embodiment, the baffle tube 216 is formed morenarrowly than the baffle tube 16 depicted in FIG. 1 so as to define arelatively close space 300 with the outer surface of the reference tube214, thereby enabling efficient scrubbing of the reference tube 214 forbetter heat transfer.

The embodiments depicted in FIGS. 1 and 2 have certain similarities.Thus, in both embodiments a reference member and a heat expansibleactuator member are provided. In the embodiment of FIG. 1 the valve headis carried by the expansible reference member while in the embodiment ofFIG. 2 the valve head is carried by the reference member; however, ineach case the valve head is moved as a result of the establishment of adifferential in expansion between the actuator and the reference member,the actuator being identified as such merely on the basis of it beingthe component that is more greatly expanded than the other components ofthe valve. The considerations with respect to materials of constructionand effective lengths of the various components are the same for thevalve 210 of FIG. 2 as they are for the valve 10 of FIG. 1. By theutilization of the foregoing construction, a valve head 58 or 258 can beutilized which has relatively flat tapers, thereby minimizing anytendency to clog.

While each of the above embodiments was described with a valve assemblyin which the valve is caused to open by heating of the actuator, thepresent invention also contemplates the utilization of a valve head inwhich closure of the valve is effected by expansion of the actuator,although modifications may be required, such as spring-loaded componentsfor purposes of safety. It should be noted that with the embodimentsillustrated, as long as the reference tube and actuator are maintainedat the same temperature, no stress can be applied to cause damage to thevalve head or valve seat.

By utilization of the innovational designs described herein, a valve isprovided which is small, lightweight, rugged and inexpensive. The valveworks in a stable and precise manner over a very large range of fluidflows. For example, units have been built which can control the flow offrom 50 to 3,000 cubic centimeters per minute of gaseous fluid. Thevalve is designed for screw-in utilization so that units can be replacedvery readily. The valve is hermetically sealed and requires no movingpacking glands or the like and can be thus used for the control andmetering of dangerous or exotic gases such as silane, 'arsine, or thelike. Operation is frictionless allowing the valve stroke to be madevery small, on the order of microinches, enabling the utilization of aflat valve head to minimize the chances of clogging. The presentconstruction requires only little power, the heating element directlycoupling to a control signal output amplifier. Thus, there has beenprovided an electromechanical transducer without a motor or solenoid inwhich there is virtually no wear or friction.

The foregoing exemplary embodiments have been described as controllingfluid from the reference tube to the actuator. However, it should berecognized that a reversal of this arrangement can be utilized forspecific desired purposes. Thus, by reversing the fluid flow with any ofthe foregoing embodiments, convective heat transfer from the actuator tothe reference tube is magnified. This provides a dynamic lead functionupon change in fluid flow. For example, in systems where the controlsignal is a function of fluid flow, the magnification can effect amovement of the valve head prior to control signal therefor. Otherexamples will now be evident to those skilled in the art.

I claim:

1. A thermal valve comprising:

an elongated reference member and an elongated heat-expansible actuatormember, each of substantially identical coefficients of heat expansion,one of said members being disposed coaxially about the other of saidmembers;

a valve assembly having a movable component operatively associated withsaid other member;

an elongated baffle coaxially between said actuator member and saidreference member;

means including inlet and outlet ports for directing fluid through saidvalve assembly in one direction in contact with and from said referencemember on one side of said baffle to another direction to contact saidactuator member on the other side of said baffle;

means for heating said actuator member whereby to effect a differentialin expansion between said actuator member and said reference member; and

means for rigidly interconnecting said actuator member and saidreference member at a common end spaced from said valve assembly wherebysaid expansion differential effects movement of said one member tooperate said valve assembly.

2. The invention according to claim 1 including means for generating acontrol signal for said valve, means for amplifying said control signal,and means for applying said amplified signal to said heating meanswhereby to heat said actuator member in proportion to said signal.

3. The invention according to claim 1 in which said baffle is formed todirect fluid along said reference member for heat transfer therewith.

4. The invention according to claim 1 in which said baffle is formed toeffect radiant heat shielding between said actuator member and saidreference member.

5. The invention according to claim 1 in which said baffle is formed toreduce convective heat transfer between fluid in said valve and saidactuator.

tially identical effective lengths.

9. The invention according to claim 1 in which said one member comprisesa tube disposed coaxially about the other of said members.

10. The invention according to claim 9 in which said baffle is anelongated tube coaxially between said actuator member and said referencemember.

1. A thermal valve comprising: an elongated reference member and anelongated heat-expansible actuator member, each of substantiallyidentical coefficients of heat expansion, one of said members beingdisposed coaxially about the other of said members; a valve assemblyhaving a movable component operatively associated with said othermember; an elongated baffle coaxially between said actuator member andsaid reference member; means including inlet and outlet ports fordirecting fluid through said valve assembly in one direction in contactwith and from said reference member on one side of said baffle toanother direction to contact said actuator member on the other side ofsaid baffle; means for heating said actuator member whereby to effect adifferential in expansion between said actuator member and saidreference member; and means for rigidly interconnecting said actuatormember and said reference member at a common end spaced from said valveassembly whereby said expansion differential effects movement of saidone member to operate said valve assembly.
 2. The invention according toclaim 1 including means for generating a control signal for said valve,means for amplifying said control signal, and means for applying saidamplified signal to said heating means whereby to heat said actuatormember in proportion to said signal.
 3. The invention according to claim1 in which said baffle is formed to direct fluid along said referencemember for heat transfer therewith.
 4. The invention according to claim1 in which said baffle is formed to effect radiant heat shieldingbetween said actuator member and said reference member.
 5. The inventionaccording to claim 1 in which said baffle is formed to reduce convectiveheat transfer between fluid in said valve and said actuator.
 6. Theinvention according to claim 1 including means for hermetically sealingsaid valve whereby to prevent fluid flow thereinto except through saidports.
 7. The invention according to claim 1 in which said valveassembly comprises a valve head carried by said other member and a valveseat for said valve head.
 8. The invention according to claim 1 in whichsaid reference member and said actuator member have substantiallyidentical effective lengths.
 9. The invention according to claim 1 inwhich said one member comprises a tube disposed coaxially about theother of said members.
 10. The invention according to claim 9 in whichsaid baffle is an elongated tube coaxially between said actuator memberand said reference member.